Staphylococcal enterotoxin D production by Staphylococcus aureus FRI 100.

Staphylococcus aureus FRI 100 is commonly used as a control strain for staphylococcal enterotoxin A (SEA) assays. When FRI 100 was used in PCR-based enterotoxin detection methods, the strain gave a positive result for both SEA and staphylococcal enterotoxin D (SED). Production of SED was confirmed by testing concentrated and unconcentrated culture supernatants with the TECRA staphylococcal enterotoxin visual immunoassay. SED was detected after 24 h of growth in Trypticase soy broth. Primers were created to amplify the entire sed gene by PCR for subsequent sequencing. The sequenced gene showed high similarity to a previously sequenced sed gene. The SED-like gene in FRI 100 exhibited four point mutations and two deletions. Changes in the FRI 100 open reading frame altered the primary structure of the SED-like protein, allowing for coding of only the first 150 amino acids followed by a stop codon. Because the SED active site is at the proximal end, where there was no change in DNA sequence, we conclude FRI 100 produces a variant form of SED. It is necessary to note that, when using FRI 100 as an SEA control strain, it does produce a variant of the SED protein, which exhibits immunological activity, and the sed-like gene is detected by commonly used PCR primers. This phenomenon may be an important general consideration when using PCR to characterize strains of toxin-producing S. aureus. S. aureus enterotoxin-positive PCR results should be confirmed by immunological techniques.

Hunger-induced finickiness in humans.

Two experiments were conducted to examine the effect of hunger on finickiness in humans. Subjects (a total of 157 undergraduate female dieters and non-dieters) were food-deprived and then subsequently either given a snack (not-hungry group) or left food-deprived (hungry group) before being given ad libitum access to either good-tasting or bad-tasting (quinine-adultered) milkshake. Common sense predicted that hungry subjects would drink more milkshake than would not-hungry subjects, regardless of milkshake palatability. Hungry subjects did in fact drink more of the good-tasting milkshake than did not-hungry subjects, but they also drank less of the bad-tasting milkshake. We discuss possible reasons why hunger might increase rejection of bad-tasting food, as well as the limiting conditions of the effect.

Iron loading and endocrine functions in nontransfused patients with beta-thalassemia intermedia or sickle-cell thalassemia.

Body iron stores and endocrine functions were determined in eight patients with chronic hemolytic anemia who had received only small amounts of blood and no iron preparations. Four patients had beta-thalassemia intermedia (BTI) and four had sickle-cell thalassemia (SCT). Hemoglobin levels and degrees of hemolysis were similar in both groups of patients. The patients with BTI showed clear evidence of iron overload, whereas there was no evidence of iron accumulation in the patients with SCT. The three patients with BTI who had endocrinologic evaluations showed endocrine dysfunctions. Two patients with SCT had no endocrine abnormalities and the other two probably had some degree of primary hypogonadism. Iron overload in patients with thalassemia probably results from excessive intestinal iron absorption and can damage various parenchymal and endocrine organs, even in the absence of an external source of iron.